Keyboard switch means



Dec. 29, 1970 FRENKEL 3,551,865

KEYBOARD SWITCH MEANS Filed Aug. 20, 1968 oxsm/ma w .00/ 0- AW we M/VE/VTOR ATTORNEY United States Patent 3,551,865 KEYBOARD SWITCH MEANS Amotz Frenkel, Lansdale, Pa., assignor to Transducer Systems, Inc., Willow Grove, Pa., a corporation of Pennsylvania Filed Aug. 20, 1968, Ser. No. 754,067 Int. Cl. H01f 21/06 US. Cl. 336--130 9 Claims ABSTRACT OF THE DISCLOSURE A pushbutton operated switch for a keyboard comprising a pushbutton mounted on a member of magnetic metal, a proximity transducer mounted beneath the member with the end of the core of the transducer being in closely spaced relation with the member, and spring means normally holding the member in spaced relation with the core but permitting the member to be moved toward the core. When the pushbutton is pressed the member is moved closer to the core of the transducer so as to increase the electrical output of the transducer.

The keyboards of computers and other electrically operated equipment generally use contact type switches operated by pushbuttons on the keyboard. When the pushbuttons are pushed, the switches are opened or closed to control the flow of current to the mechanism of the equipment being controlled by the pushbutton. All presently known contact type switches have many limitations, such as contact wear, surface corrosion of the contacts, nolse level, speed of operation, wear of mechanical linkages, and adverse effects of external environmental conditions. Thus, the usable life of such contact switches is generally less than the usable life of the equipment being controlled so that it is often necessary to replace or repair the switches from time to time during the life of the equipment.

The pushbutton of the present invention includes a proximity transducer having a core. A member which may be of a magnetic metal is mounted adjacent to one end of the core. The member is supported on a spring which in its normal position holds the member in closely spaced relation with respect to the core of the transducer, but permits movement of the member toward the core. A pushbutton is mounted on the member whereby the member can be moved toward the core of the transducer, The transducer is of the type that provides an increase in electrical output when the member is moved closer toward the core. Thus, when the pushbutton is pressed, the member is moved closer to the core of the transducer so as to provide an increase in the electrical output of the transducer. This electrical signal can be used to operate a mechanism 'being controlled by the switch. The switch can be connected on a panel with the pushbutton projecting through a hole in the panel.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a side view of a panel having the switch of the present invention mounted thereon.

FIG. 2 is a graph showing the electrical characteristics of a proximity transducer of the type utilized in the switch of the present invention.

FIG. 3 is a schematic circuit diagram of a proximity transducer of the type utilized in the switch of the present invention.

FIG. 4 is a transverse sectional view of a modification of the switch means of the present invention.

Referring to FIG. 1 of the drawings there is shown a 3,551,865 Patented Dec. 29, 1970 panel 10 having an opening 12 therethrough. A leaf spring 14 is positioned beneath the panel 10. One end 16 of the leaf spring 14 is secured to the panel 10, such as by a rivet 18, at a point adjacent to but spaced from the opening 12. The spring 14 has a bend 20 adjacent to the end 16 so that the free end 22 of the spring 14 extends substantially parallel to but slightly spaced from the undersurface of the panel 10. A downwardly extending depression 24 is provided in the free end 22 of the spring 14 directly under the opening 12 in the panel 10. A pushbutton 26 is mounted on the free end 22 of the spring 14 and projects through the opening 12 in the panel 10.

A proximity transducer 28 is mounted beneath the free end 22 of the spring 14 with the core 30 of the transducer 28 being adjacent to but slightly spaced from the bottom surface of the depression 24 in the spring 14. The construction of a proximity transducer is well known to those skilled in the art. As shown in FIG. 3, such a transducer includes the core 30, a primary winding 32, and a pair of secondary windings 34a and 34b. The primary winding 32 has a pair of input terminals 36a and 36b. The secondary windings 34a and 34b are electrically connected in bucking arrangement and have a pair of output terminals 38a and 38b. The secondary windings 34a and 34b are electrically coupled to the primary winding 32 through the core 30 so that an electrical input to the primary winding 32 produces an electrical output from the secondary windings 34a-and 34b. With the electrical input to the primary winding 32 being held constant, the output from the secondary windings 34a and 34b can be increased by bringing a member of magnetic materials, such as the spring 14, into close proximity to the end of the core 30. The closer the member is brought to the core 30 the higher the output from the secondary windings 34a and 3412. FIG. 2 is av graph from a typical proximity transducer showing the output voltage of the transducer 28 for various distances between the core 30 and the magnetic member. As can be seen from this graph, a small movement of the spring 14 toward the core 30 can cause a relatively large incraese in the electrical output of the transducer 28.

In the operation of the switch of the present invention, an electrical input is applied to the primary winding 32 of the transducer 28, and the output terminals 38a and 38b are electrically connected to a mechanism to be controlled so that an increase in the output of the transducer 28 will operate the mechanism. Thus, when the pushbutton 26 is pressed downwardly, the spring 14 is moved closer to the core 30 of the transducer 28. This provides an increase in the output of the transducer 28 so as to operate the mechanism. To ensure that the same output of the transducer 28 is obtained each time the pushbutton 26 is pushed, the switch may be provided with means for limiting the movement of the spring 14 toward the core 30 of the transducer 28. As shown in FIG. 1, such a stop means can comprise a bracket 40 second to the undersurface of the panel 10 and extending downwardly across the free end of the spring 14. The bracket 40 has a ledge 42 at its bottom end which extends beneath the free end of the spring 14. A screw 44 is threaded through the ledge 42 and extends toward the spring 14.

' Thus, each time the pushbutton 28 is pressed, the spring 14 will engage the end of the screw 44 so as to obtain a uniform output from the transducer 28. By properly positioning the screw 44, an output can be obtained from the transducer 28. Thus, the stop means not only provides a uniform output of the transducer 28, but also permits an adjustment of the output.

Thus, there is provided by the present invention of a switch which has no moving or contacting parts which can become worn, corroded or otherwise damaged so as to adversely affect the operation of the switch. Although the spring 14 moves, the extent of its movement is so small that the spring 14 has an extremely high cycle life, 10,000,000 or more, Also, the switching characteristics of the switch cannot be adversely alfected by external environmental conditions. In addition, the output of the switch can be either an AC. signal or a detected DC. signal so that the switch can be used to operate any type of mechanism. Thus, the switch of the present invention will have an operating life as long as that of the equipment in which it is to be used. Although FIG. 1 shows a panel having only one switch of the present invention, it should be understood that the panel can contain any desired number of the switches according to the requirements of the equipment being controlled.

Referring to FIG. 4, a, modification of the switch means of the present invention comprises a cup-shaped housing 46 having a cylindrical wall 48 and a base 50 extending across one end of the wall 48. The base 50 has a hole 52 extending through the center thereof, and a cylindrical boss 54 projects upwardly from the base 50 around the hole 52. A proximity transducer 56 is secured in the hole 52 with the end of the core 58 of the transducer 56 being positioned at the upper end of the boss 54. The transducer 56 is of the same type as the transducer 28 of the switch means shown in FIG. 1.

A pushbutton 60 is positioned in the upper, open end of the housing wall 48. The outer diameter of the pushbutton 60 is smaller than the inner diameter of the hous ing wall 48, and an annular flange 62 projects radially from the bottom end of the pushbutton. A retainer ring 64 is secured in the upper end of the housing wall 48. The retainer ring 64 extends around the pushbutton 60 and over the flange 62 of the pushbutton. A disk 66 of a magnetic metal is secured to the bottom surface of the pushbutton 60. A helical spring 68 surrounds the boss 54 and is compressed between the disk 66 and the housing base 50. The spring 68 normally presses the disk 66 and the pushbutton 60 upwardly until the pushbutton flange 62 engages the retainer ring 64.

In the use of the switch means 46 the spring 68 normally holds the disk 66 away from the core 58 of the transducer 56. When the pushbutton 60- is pressed downwardly, the disk 66 is moved toward the core 58 and thereby increases the electrical output of the transducer 56 in the manner previously described with regard to the switch means of FIG. 1. If desired, the switch housing 46 can be mounted on a panel with the pushbutton 60 projecting through an opening in the panel.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

What is claimed is:

1. A switch means comprising a proximity transducer having opposite ends, having a primary winding for receiving an alternating energizing signal, a secondary winding with sections connected in opposing relationship, said primary and secondary windings being about a core opening and a fixed magnetic core within said core opening, extending the full length of the primary and secondary windings, having an end at one end of said transducer; a member of metallic material; and means positioning said member external to said transducer and normally in closely spaced relation with respect to the end of the core of said transducer while permitting movement of said member for changing its spacing with the end of said core; the secondary winding of said transducer providing a change in electrical output when said member is moved with respect to said core,

2. Means in accordance with claim 1 in which said means positioning said member comprises a spring per- 4 mitting movement of said member from its normal position toward the end of the core of said transducer.

3. Means in accordance with claim 2 in which said spring is a leaf spring fixedly supported at one end and positioning said member at its other end.

4. Means in accordance with claim 2 in which the secondary Winding of said transducer provides an increase in electrical output when said member is moved toward the end of the core of said transducer.

5. Means in accordance with claim 1 including a housing having an opening therein, said transducer being received within the opening of said housing, said member positioning means comprising a coil spring received within the openng of said housing having an end proximate to the transducer and another end proximate to said member.

6. Means in accordance with claim 5 including a pushbutton received at least partially within the opening of said housing and having an externally exposed end and an internal end engaging said member, said housing being provided with retaining means for retaining said pushbutton within the opening of said housing while allowing the pushbutton to slide within the housing for compressing said spring and moving said member toward said transducer.

7. A switch comprising a proximity transducer having opposite ends, having a primary winding for receiving an alternating energizing signal, a secondary winding with sections connected in opposing relationship, said primary and secondary windings being about a core opening, and a fixed magnetic core within said core opening, extending the full length of the primary and secondary windings, having an end; a member of metallic material; spring means normally holding said member in closely spaced relation with respect to the one end of the core but permitting movement of said member toward said core; said transducer providing an increase in electrical output when the member is moved closer to the core; a panel having an opening therethrough; said spring means being a leaf spring with an end secured to the panel adjacent to but spaced from the opening and another end extending across the opening in the panel; and a pushbutton mounted on the other end of the spring and projecting through the opening in the panel.

8. Means in accordance with claim 7 including a stop means engageable by the other end of the spring to limit the movement of the other end of the spring toward the core of the transducer.

9. Means in accordance with claim '8 in which the stop means comprises a bracket secured to the undersurface of the panel and extending across the other end of the spring, a ledge extends from the end of the bracket beneath the other end of the spring, and a screw is threaded through the ledge and extends toward the other end of the spring.

References Cited UNITED STATES PATENTS 2,507,344- 5/1950 Macgeorge 33 6--136X 2,881,402 4/1959' Walker 336136 3,054,976 9/ 1962 Lipshutz 336-136 3,210,746 10/1965 Clapp 336--l36X 1,242,778 10/1917 Darling 336-136X 2,210,970 8/ 1940 Bonell 336-136X 2,913,688 11/1959 Slebodnik et al. 336-'X 3,199,056 8/1965 Cameron 336-130 3,328,734 6/1967 Harmon 3116-136X THOMAS J. KOZMA, Primary 'Examiner US. Cl. X.R. 336-134; 340-365 

